Current methods of analyzing human ascites do not always distinguish cancer from benign diseases. Studies were undertaken to assess the feasibility of measuring CEA-activity in these fluids by a modified zirconyl-phosphate gel (Z-gel) radioimmunoassay as an aid to detection of colo-rectal cancer. These studies suggest that CEA or CEA-like material is present in malignant effusions and may be differentiated from non-CEA like material in benign fluids by quantitative and/or qualitative evaluation in the radioimmunoassay. Assay of CEA-activity in effusions may be an adjunct to cytology in the detection of colo-rectal cancer. We are expanding our studies to: (a) evaluate the range of values found, (b) correlate tumor morphology and CEA levels, (c) study the relationship between CEA-activity and protein components in the fluids, and (e) immunochemically characterize the CEA-active material(s) and compare it with purified CEA prepared from colonic malignancies. BIBLIOGRAPHIC REFERENCES: Loewenstein, M.S. Rittgers, R.A., Kupchik, H.Z. Feinerman, A.E. and Zamcheck, N.: Improved detection of malignant ascites and pleural effusions by combined assay of fluid CEA and cytology. Clin. Res., 23; 253A, 1975.